In a brutal assessment of the former party leader, the social mobility tsar said the party “could not have got it more wrong” in its fight for No 10.

In a speech to the right-wing Centre for Social Justice, a think tank founded by Work and Pensions SecretaryIain Duncan Smith, he suggested voters were put off after the party “bet the house on the country moving to the left.”

However, support for Jeremy Corbyn’s campaign has continued to soar online.

Almost 30,000 people now like his Facebook page and 10,500 follow his campaign on Twitter.

And Mr Corbyn was the only Labour leadership candidate not to be booed at the first official Labour hustings in Stevenage on Saturday.

Ms Kendall and his other rivals, Andy Burnham and Yvette Cooper, angered supporters by refusing to rule out supporting Tory plans to cut the benefit cap from £26,000 a year to £23,000.

Mr Corbyn’s campaign team is now calling on social media socialists to sign-up as party supporters, which costs £3, and vote for the left candidate.

LIZ KENDALL makes a bold attempt to appeal to the left in her article for today’s Morning Star.

The Leicester West MP is to be congratulated on her willingness to address the readers and supporters of a newspaper that has made no secret of its hostility to the secretive, billionaire-backed Progress faction she belongs to, or to the Blairite brand of politics she represents.

Unfortunately, her article is as noteworthy for what it doesn’t say as for what it does.

She slams the Tories for their “ideological crusade against the state and our public services.” Yet this is the MP who as shadow health minister praised the “important role” of private-sector companies in the National Health Service back in January, a stance which contrasted with that of Andy Burnham — then her boss as shadow health secretary — and won praise from Tory Health Secretary Jeremy Hunt.

She is in favour of the academies and free schools drive, which removes schools from local accountability, allows the use of unqualified teachers in the classroom and helps break down collective bargaining structures for the profession — giving the lie to her demand that we “give our public service workers the decent pay rise they need.”

Kendall is apparently outraged that the Conservatives are pursuing policies that “are more about punishing the poor than balancing the books,” but she supported the Tories’ arbitrary welfare cap on households and even says she agrees with the restriction of child benefit to the first two children.

Politics is about two things, she tells us — “the principles that sustain us and winning elections so that we can put those principles into practice.”

Her emphasis is apparently all on the latter, without any of the subtlety of Lenin’s “without revolutionary theory there can be no revolutionary movement.”

But we should be wary of accepting Kendall’s premises for the argument that “we can only truly act on our values when we win the support of the country.”

For one thing, a Labour government which implements the agenda of the rich minority — privatisation, outsourcing, war — does not help working people, will lose their support and prepares the ground for a more radical Conservative assault later on.

The last Labour government began the academies drive, let the private sector into the NHS and attempted to sell Royal Mail. Policies either accelerated or brought to fruition by its Tory successors.

For 13 years it left trade unions shackled by a raft of anti-democratic restrictions on their activity, paving the way for the shocking bid to make strike action impossible by the current government.

These decisions did untold damage to our welfare state and workers’ rights. They also did serious damage to Labour’s reputation, meaning it was unable to credibly oppose Tory policies it had followed itself when in power and did not look like a serious alternative in May.

So Kendall’s “two things” that make up politics, principles and power, are not discrete entities between which her party must strike a balance. They are intimately intertwined.

Labour is not the Conservative Party. It is not bankrolled by the super-rich and does not have the inherent advantages of a party of wealth and power — a cheerleading press, a bottomless treasure chest, the tacit sympathy of all the institutions of the British state.

It is, to quote the Labour leader who won more elections than any other — Harold Wilson — a moral crusade or it is nothing. That is, its success or failure relies on whether it can mobilise and express the aspirations of a mass movement far larger than the party itself.

And when it comes to that, Kendall’s Tory-lite politics just don’t cut it, however attractive her rhetoric about reviving people power, trade unions and co-operatives.